Pair programming is a simple, straightforward concept. Two programmers work side-by-side at one computer, continuously collaborating on the same design, algorithm, code, and test. It produces a higher quality of code in about half the time than that produced by the summation of their solitary efforts. However, nothing is simple where people and personalities are involved - especially people who are accustomed to working alone. The leap to pair programming for a variety of software development projects is one that yields many benefits, but it is also one that requires careful thought and planning. Written as instruction for team members and leaders new to pair programming, and as an improvement guide for experienced pair programmers, Pair Programming Illuminated explains both the principles underlying this method and its best practices. The authors, drawing on their own extensive experience, explain what does and does not work, what should be emphasized, and what should be avoided. Two case studies further illuminate pair programming in practice: one in the context of Extreme Programming (XP), with which it often is associated, and one linked to a more disciplined software engineering process.